Method and apparatus for producing swept frequency-modulated audio signal patterns for inducing sleep

ABSTRACT

A method of producing sound signals for inducing sleep in a human being, and apparatus therefor together with REPRESENTATIONS thereof in recorded form, wherein an audio signal is generated representing a familiar, pleasing, repetitive sound, modulated by continuously sweeping frequencies in two selected frequency ranges having the dominant frequencies which occur in electrical wave patterns of the human brain during certain states of sleep. The volume of the audio signal is adjusted to mask the ambient noise and the subject can select any of several familiar, repetitive sounds most pleasing to him.

United States Patent Zentmeyer, Jr. 1 1 Jan. 23, 1973 [54] METHOD ANDAPPARATUS FOR 3,140,709 7/1964 Weisz ..12s 1 R PR DUCING W PT R U Z ES EFORElGN PATENTS OR APPLICATIONS PATTERNS FOR INDUClNG SLEEP 1,165,541 101969 Great Britain ..128 1 0 [75] Inventor: John E. Zentmeyer, Jr.,Charlot- Primary Examiner wimam BKamm tesvlue Att0rney-Thomas B. VanPoole et al.

[73] Assignee: Karen V. Lafley, Charlottesville,

[57] ABSTRACT [22] Filed; July 20, 1971 A method of producing soundsignals for inducing sleep in a human being, and apparatus therefor 1 vNW 164,389 together with REPRESENTATIONS thereof in recorded form,wherein an audio signal is generated 52 U.S. c1. ..12s/1c familiar,Pleasing repetitive Sound, [51] Int. CL I I I I A61 1/34 modulated bycontinuously sweeping frequencies in [58] Field of i 179/1 AA twoselected frequency ranges having the dominant frequencies which occur inelectrical wave patterns of the human brain during certain states ofsleep. The [56] References cued volume of the audio signal is adjustedto mask the am- UNITED STATES PATENTS bient noise and the subject canselect any of several familiar, repetitive sounds most pleasing to him.3,014,477 12/1961 Carlin ..l28/l C 2,304,095 12/1942 Hull ..l28/l C 13Claims, 2 Drawing Figures LOUD SPEAKERDU to 1 1'2 28 5AM: SOUNDGENERATOQ M\XE |2 AMP. (OcocmSuvf) I 4 48 I6 4e 4 LEVEL AUTO 1 iST-I'Z6o. ADJUST 1 SIGNAL MIXER 26b I GENERATOR 4 26 TO OTHER 1 20 a 22AND 26 Mmes SPLITTER Pow. o-ruea FREQUENCY J SOUNDS VARYING DEVlCE. 1 8t 24 i l l 8 2ND Mo 1 lGNAL E GENE-R9302 METHOD AND APPARATUS FORPRODUCING SWEPT FREQUENCY-MODULATED AUDIO SIGNAL PATTERNS FOR INDUCINGSLEEP BACKGROUND AND OBJECTS OF THE INVENTION The present inventionrelates in general to a method and apparatus for producing sounds forinducing sleep in a human being, and more particularly to a method andapparatus for producing sleep inducing sounds by the generation ofcomposite audio signal patterns formed by modulating a familiar,pleasing, repetitive sound with continuously sweeping frequencies infirst and second frequency ranges resembling electrical wave patterns ofthe human brain during certain states of sleep.

The use of audio generators to induce sleep has been previously known,as for example in U. S. Pat. Nos. 2,711,165 and 3,384,074, wherein audiosignals are generated which represent pleasing and harmonious steadysounds or cyclically varying repetitive sounds resembling sounds foundin nature or in the normal environment of the individual. It has alsobeen proposed to induce sleep by the generation of an audio signal whichis varied at a rate somewhat slower than the rate of heartbeat orrespiration to tend to cause the heartbeat and respiration of theindividual to synchronize with the audio signal.

It has also been proposed to induce sleep by generating an audio signalwhich is a familiar, pleasing, repetitive sound modulated by a selectedfixed frequency which is found in an electroencephalographic sleeppattern produced by the human brain during sleep, for examplebymodulating the pleasing sound with what are termed theta waves havinga frequency of 6 cycles per second (cps) and with a wave of sleepspindles which are short bursts of waves at a frequency of about 14 cps,the modulating signal also including delta waves having a frequency of lcps such as occur in the EEG sleep pattern for stage-3 and stage-4sleep. However, it has been found that the frequency of the delta wavesin the EEG sleep pattern for different individuals may occur anywherewithin the frequency range of about 0.8 cps to 1.8 cps, and that aperson whose EEG sleep pattern has a delta wave frequency within thisrange which does not precisely coincide with 1 cps does not respondeffectively to the composite sleep inducing signal. The same sharpfrequency response characteristic is found to be true of theta waveresponse.

An object of the present invention is the provision of a method andapparatus for producing signals for inducing sleep in a broad spectrumof different individuals, wherein a familiar, repetitive, pleasing soundis modulated by a first modulation signal whose frequency iscontinuously swept through a first preselected frequency range and isalso modulated by a second modulation signal which is continuously sweptthrough a second frequency range, which frequency ranges include thefrequencies of certain EEG electrical wave signals encountered duringsleep.

Another object of the present invention is the provision of a method andapparatus for producing signals for inducing sleep as .described in thepreceding paragraph, wherein the first modulation signals are sweptthrough a frequency range of about 0.8 to 1.8 cycles per second and thesecond modulation signals are swept through a frequency range of about5.5 to 6.75 cycles per second.

Other objects, advantages and capabilities of the present invention willbecome apparent from the following detailed description, taken inconjunction with the accompanying drawing illustrating apparatus whichmay be employed to produce the sleep inducing sounds.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram of one systemthat may be used to generated the sleep inducing sounds in accordancewith the present invention; and

FIG. 3 is a block diagram of another system that may be employed toproduce the sleep inducing sounds.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Anelectroencephalogram (EEG) is a device for measuring the flucuation ofelectrical potentials due to the electrical activity of the brain. Ithas been found through the use of the EEG that various patterns ofelectrical potentials are generated for different states ofconsciousness. The primary states that can be distinguished are thestates of waking and sleeping. Within the waking state, one candistinguish various degrees of activation or alertness, ranging fromrather frantic hyperaltertness through relaxed attentiveness todrowsiness. Extreme alertness is associated with a low voltage,generally fast and irregular pattern of about 10 to 20 microvoltsamplitude and frequencies ranging from 10 to 40 cycles per second (cps).Relaxed alertness is accompanied in many people by the alpha rhythm, arather irregular, sinusoidal rhythm whose frequency varies from about 8to 13 cycles per second, although in a single person this frequency isrelatively constant. As a person becomes drowsy, this alpha rhythmbreaks up, clusters of it becoming less and less frequent as they arereplaced by a stage-l drowsy pattern.

The EEG pattern for the first state of sleep, or stage- 1 sleep,consists of an irregular mixture of theta waves which are low inamplitude and have a frequency lying in the range between 4 and 8 cps,the mixture of theta waves being accompanied by occasional alpha wavesand irregularly appearing alphoid waves, which are waves similar to thealpha rhythm waves but I or 2 cps slower than the subjects waking alpharhythm.

The EEG pattern for stage-2 sleep, wherein sleep is definitely present,is similar to the stage-1 drowsy pattern except that a new kind of wavepattern, termed the sleep spindle, appears. The sleep spindle is a shortburst of waves at about 14 cps frequency, which starts at a very lowamplitude, builds up to about 30-40 microvolts within a few cycles, andthen tapers off, giving the overall wave train a spindle shape.

Sleep is further divided into stage-3 sleep and stage-4 'sleep. Thesestages are characterized by the appearance of delta waves, which arerelatively high voltage waves of an amplitude of microvolts or more, andhave a relatively low frequency of about I cps or slower. A few of thesedelta waves in the EEG pattern characterize stage-3, while apreponderence of them characterize the EEG pattern for stage-4 sleep. Instage3 sleep and stage-4 sleep, the spindles and irregular theta wavescontinue to occur.

It has been recognized that various sensory inputs to the human bodytended to produce relaxation, drowsiness and sleep. For example, thesensation of gentle rocking produces relaxation and sleep in somesubjects tested. Eye fixation and fatigue have been most productive inbringing on drowsiness, but the effect did not continue or heightenbeyond eye closure to any appreciable extent. Generation of audiblesounds to provide sleep inducing inputs to the aural sense offers anumber of advantages. The aural sense organ is the only body-perceptormechanism that continues to function into the various stages of sleep aswell as during relaxation and drowsiness. It has been determined thatthis sense of hearing functions not only in the first three stages ofsleep, but functions to some degree in stage-4 sleep and into stages ofanaesthesia. Also, induction of sleep by aural means permits greatersubject control, as the process of sleep induction can be reversed orterminated with relative ease and promptness.

Certain familiar, repetitive, non-objective sounds or noises, such ascertain sounds of nature or environmental sounds, tend to producedrowsiness and sleep. Conversely, the lack of such sounds tends toproduce alertness and wakefulness. Thus a city dweller may sleep deeplywith the steady rumble of traffic outside, but the sound of countrycrickets may sound so noisy to him that he cannot sleep. Each individualis receptive to certain sound patterns which are the product of hisenvironmental conditioning, which will tend to produce relaxation andsleep. The most common of these to produce sleepiness are familiar,repetitive sounds such as rain on the roof, machinery hum, gentle wind,ocean surf, breathing, and heartbeat, to name a few examples.

Experiments have been conducted to attempt to induce sleep by an auralsignal formed by amplitude modulating any of the pleasing repetitivesounds, as selected by the subject, with delta waves at a frequency of lcps resembling the waves which characterize the EEg pattern for stage-3sleep, together with theta wave signals at a specific frequency, forexample 6 cps, resembling the theta waves that occur in the EEG patternfor stage-1 or stage-2 sleep. For certain subjects, the results achievedby inducing sleep with such a signal were several magnitudes higher thaninduction of sleep by use of a pleasant sound only. However, it wasdiscovered that the human brain acts in its response to the modulationfrequencies in the aural signal in a manner similar to a highly tuned,sharp frequency response tank circuit, in that the particular frequencyof the delta wave and theta wave modulation signals to which differentindividuals will responds to induce sleep will depart somewhat from thel cps and 6 cps delta and theta wave frequencies employed to modulatethe pleasing repetitive sound. To achieve reliable induction of sleep ina broad spectrum of individuals whose EEG patterns may be characterizedby delta waves and theta waves whose frequencies may be different fromthe l cps and 6 cps frequencies, the present invention involves themodulation of the basic familiar, repetitive, pleasing sound with amodulation signal which comprises delta wave signals which arecontinuously swept back-andforth in frequency between 0.8 cps and 1.8cps and with theta wave signals which are continuously swept infrequency back-and-forth between 5.5 cps and 6.75 cps. By continuouslysweeping the frequencies of the delta wave and the theta wave signalsback-and-forth within these ranges, there will be delta waves and thetawaves of the specific.

repetitive sound which would be pleasing to the individual. Typically,the basic sound for a person living in an urban environment would be thesound of rain on a roof, a gentle wind, waves upon a beach, slowbreathing, machinery hum, ocean surf, or similar examples. Preferablythe individual desiring to have sleep. induced should have the option ofselecting which of such basic sounds should be produced. This basicsound in the form of a pleasing repetitive sound is modified, forexample by amplitude modulating or mixing or both with a first modifyingsignal which is continuously swept back-and-forth in frequency between0.8 cps and 1.8 cps, and is also modified, by modulation or mixing orboth with a second modifying signal which is continuously sweptback-and-forth in frequency between 5.5 cps and 6.75 cps, torespectively resemble the basic frequencies found in the delta wavepatterns and theta wave patterns of EEG sleep signals. In one example,the amplitude of the first modifying signal is about microvolts and theamplitude of the second modifying signals is about 100 microvolts.

The sleep inducing audio signals produced at the bedside of the subjectdesiring to have sleep induced may be produced by providing magnetictapes or similar records on which are recorded the desired sleepinducing sounds, which tapes or other records are placed in a suitableconventional reproducer or playback device to produce audio outputsignals responsive to the tape or other sound record. Alternately, anaudio generator may be provided in the room occupied by the individualwhich has the capability of providing the different basic familiar soundpatterns to be selected by the individual, and the audio generator isprovided with means for modifying the pleasing, repetitive soundsselected by the subject as the basic sound pattern, with modifyingsignals like the first and second varying frequency modifying signalsdescribed in the preceding paragraph, to produce the composite signalwhich includes signals sweeping back-and-forth in frequency between 0.8and 1.8 cps and between 5.5 and 6.75 cps. Also, a central soundgenerator system including an audio generator and the modulation meansas described above may be provided at a central location in a multipleroom housing facility, such as a motel or hotel or an apartmentbuilding, and the output central sound generating device may be coupledto speakers or transducers in each of the rooms to be operated by theindividual occupants to make the selection of the basic repetitivesignal desired.

The volume level of the device used to produce the sleep inducing soundsat the location of. the individual desiring to have sleep induced shouldbe adjusted to be sufficient to mask the ambient noise in theenvironment of the individual. This is accomplished by setting thevolume level of the sleep inducing sounds to a particular level andlistening for several moments to extraneous noise, and then adjustingthe loudness of the sleep inducing sound patterns so that the extraneousor environmental noises are not intrusive or cannot be heardconsciously. Also, a timing device may be employed in conjunction withthe means for producing the sleep inducing sounds at the location of theindividual to determine the number of hours the individual desires tosleep, so as to terminate production of the sleep inducing soundpatterns at the end of the desired period.

One examples of a portion of apparatus for producing sleep inducingsounds in accordance with the present invention is illustrated in blockdiagram form in FIG. 1. Referring to FIG. 1, there is shown a basicrepetitive sound generator 10, which may be any conventional soundreproducing device such as a magnetic tape reproducer or play-backdevice for producing an audio frequency output responsive to a magnetictape or cassette recording of a basic repetitive sound, such as thesound of ocean surf, or any of the other six previously mentioned basic,familiar, repetitive sounds. Alternatively, the basic sounds can beproduced electronically. The output signals from the repetitive soundgenerator are applied to one input of a conventional mixer stage 12. Themodifying signal generating means are generally indicated at 14 in FIG.1, and comprises a first modifying frequency signal generator 16 capableof producing output signals at any frequency within the range .8 cps to1.8 cps, and a second modifying frequency signal generator 18 capable ofproducing output signals at any frequency within the range 5.5 cps to6.75 cps. Both of the modifying frequency signal generators l6 and 18are continuously swept back-andforth by a frequency varying device 20which may be, for example, a motor driven mechanism mechanically coupledto capacitive or inductive elements of the generators 16 and 18 to varythe frequencies thereof within the stated ranges. The outputs from themodifying frequency signal generators l6 and 18 are coupled to a signalmixer 22 where the outputs are mixed and are then supplied to isolationand splitter circuitry, indicated generally at 24, which apply the mixedfrequency signals from the output of the mixer 22 through output lead26a to the mixer 12 to modify the signals from the sound generator 10,or to apply the mixed modifying frequency signals through any of theother output leads 26b, 26c, 26d, 26e and 26f to mixers like the mixer12 associated with each of the other basic repetitive sound generatorssimilar to sound generator 10 producing the other basic familiar soundpatterns mentioned above. The output from the mixer 12 associated withthe sound generator 10, or from any of the other mixers associated withany of the other basic sound generators, is applied to a conventionalamplifier stage 28 whose output drives a speaker 44 or other soundtransducer to produce the sleep inducing sound signals. A conventionallevel adjustment control 46 may be associated with the amplifier 28 topermit variation of the volume level by the listener, and an automaticturn-off timing device 48 may be provided, to perform the functionsdescribed in the immediately preceding paragraph.

An alternate circuit arrangement for generating the sleep inducingsounds is illustrated in block diagram fonn in FIG. 2, with someassociated waveforms, wherein first and second pulse signal generatorsl6 and 18 are activated by a frequency varying device 20 to continuouslysweep the pulse frequency of the output from signal generator 16 between0.8 and 1.8 cps and to continuously sweep the pulse frequency of theoutput from signal generator 18 between 5.5 cps and 6.75 cps. Theoutputs from the two signal generators 16 and 18 are applied toflip-flop circuits 30 and 32 to trigger them and produce approximatelysquarewave outputs which are rounded off by the selection of componentvalues. Their outputs are applied to gating circuits 34 and 36, to whichthe output from a white noise generator 38 is also applied. The whitenoise produced by the generator 38 may be described as a multi-frequencysound or a sound involving all frequencies needed to mix with thepleasing basic repetitive sound such that its presence is evident whenmixed. The outputs from the gates 34 and 36, are applied throughuni-directional diodes or similar devices 40, 42 to the inputs to mixers12 associated with the basic repetitive sound generators, such as theocean surf sound generator 10, for mixing the composite signal with theoutput from the basic sound generators to produce the composite sleepinducing output signal.

It will be apparent that apparatus such as that indicated in blockdiagram form in FIGS. 1 and 2 may be provided in the bedroom of theindividual desiring to have sleep induced, or may be employed as acentral sound producing system to produce electrical signal outputswhich are coupled to transducers or speakers in the bedrooms of motels,hotels, apartment buildings and the like, or may be employed as thesound producing device to generate the sleep inducing signals which arethen recorded on magnetic tape, cassettes, or similar sound recordingrecords, by a conventional recording device, indicated at 50 in FIG. 1,which may be used in the conventional manner in sound play-back devicesowned by the individuals.

It is not established whether the modifying signals modulate the basicsound or mix with the basic sound, or both. Hence the term modifying hasbeen used herein to describe the action which occurs.

What is claimed is:

1. A method of producing signal patterns for inducing sleep in a humanbeing by audible sounds, comprising the steps of generating an audiosignal representing a familiar, repetitive, pleasing sound, generating afirst modifying signal having a varying frequency and continuouslysweeping said first modifying signal backand-forth through a frequencyrange from about 0.8 cycles per second to 1.8 cycles per second,generating a second modifying signal having a varying frequency andcontinuously sweeping said second modifying signal back-and-forththrough a frequency range from about 5.5 cycles per second to 6.75cycles per second, and modifying the audio signal with said first and Isecond swept modifying signals to produce a composite output signalrepresentative of the modified audio signal for production of an audiblesound output therefrom.

2. A method of producing sounds for inducing sleep in a human being,comprising the steps of generating an audio signal representing afamiliar, repetitive, pleasing sound, generating a first modifyingsignal having a varying frequency and continuously sweeping said firstmodifying signal back-and-forth through a frequency range from about 0.8cycles per second to 1.8 cycles per second, generating a secondmodifying signal having a varying frequency and continuously sweepingsaid second modifying signal back-and-forth through a frequency rangefrom about 5.5 cycles per second to 6.75 cycles per second, modifyingthe audio signal with said first and second swept modifying signals toproduce a composite output signal; and producing an audible sound outputfrom said composite signal for inducing sleep in an individual.

3. A method of producing sounds for inducing sleep as defined in claim2, including the further step of setting a timing device toautomatically turn off the output signal after a pre-determined time.

4. A method of producing sounds for inducing sleep as defined in claim3, comprising the further step of setting the audible level of saidsound output at a level to mask the ambient noise level of theenvironment.

5. A method of producing signal patterns for inducing sleep in a humanbeing, by audible sounds, comprising the steps of generating a selectedaudio signal chosen from a group of pre-determined audio signals,generating a first modifying signal having a varying frequency andcontinuously sweeping said first modifying signal back-and-forth througha frequency range from about 0.8 to 18 cycles per second resemblingdelta wave patterns occurring in a human EEG sleep pattern signal,generating a second modifying signal having a varying frequency andcontinuously sweeping said second modifying signal back-and-forththrough a frequency range from about 5.5 to 6.75 cycles per secondresembling theta wave patterns occurring in a human EEG sleep patternsignal; and modifying said selected audio signal with said first andsecond swept modifying signals to produce a composite output signalrepresentation of the modified audio signal for production of an audiblesound output therefrom for inducing sleep in a human being.

6. A method of producing sounds for inducing sleep in a human being,comprising the steps of generating a selected audio signal chosen from agroup of predetermined audio signals, generating a first modifyingsignal having a varying frequency and continuously sweeping said firstmodifying signal back-and-forth through a frequency range from about 0.8to 1.8 cycles per second resembling delta wave patterns occurring in ahumanEEG sleep pattern signal, generating a second modifying signalhaving a varying frequency and continuously sweeping said secondmodifying signal backand-forth through a frequency range from about 5.5to 6.75 cycles per second resembling theta wave patterns occurring in ahuman EEG sleep pattern signal, modifying said selected audio signalwith said first and second swept modifying signals to produce acomposite output signal, and producing an audible sound output from saidcomposite output signal for inducing sleep in a human being.

7. Amethod of inducing sleep as defined in claim 6, comprising thefurther step of setting the audible level of said audible sound outputat a level to mask the ambient noise level of the environment.

8. A method of producing sounds for inducing sleep in a human being,comprising the steps of generating a composite signal representation ofa familiar, repetitive, pleasing audio signal, producing a firstmodifying signal and continuously sweeping it back-and-forth through afrequency range from about 0.8 cycles per second 1.8 cycles per second,modulating said audio signal with said first modifying signal, producinga second modifying signal and continuously sweeping it back-and-forththrough a frequency range from about 5.5 cycles per second to 6.75cycles per second, modulating said audio signal with said secondmodifying signal thereby producing a composite signal representationfrom said audio signal and said modifying signals, and producing anaudible sound output from said composite signal representation forinducing sleep in an individual.

9. A method of producing sounds for inducing sleep as defined in claim8, comprising the further step of setting the audible level of saidaudible sound output at a level to mask the ambient noise level of theenvironment.

10. Apparatus for producing signal patterns for inducing sleep in ahuman being by audible sounds, comprising audio signal generating meansfor generating an audio signal representing a familiar, repetitive,pleasing sound, first and second modifying signal generators, means forvarying the frequency of the signals produced by said modifying signalgenerators for generating a first signal having a varying-frequencyrange from about 0.8 to 1.8 cycles per second and for concurrentlygenerating a second modifying signal having a varying frequency which iscontinuously swept back-and-forth through a frequency range from about5.5 to 6.75 cycles per second; and means for modifying the audio signalwith said first and second modifying signals to produce a compositeoutput signal representation of the modified audio signal for productionof an audible sound output therefrom.

11. Apparatus as defined in claim 10, including recording means forrecording said composite output signal representation on a recordingmedium.

12. Apparatus as defined in claim 10, including recording means forrecording said composite output signal representation on magnetic taperecording medi- 13. A method of producing signal patterns for inducingsleep in a human being by audible sounds, comprising the steps ofgenerating an audio signal representing a familiar, repetitive, pleasingsound, generating a first modifying signal having a varying frequencyand continuously sweeping said first modifying signal backand-forththrough the delta frequency range, generating a second modifying signalhaving a varying frequency and continuously sweeping said secondmodifying signal back-and-forth through the theta frequency range andmodifying the audio signal with said first and second signals to producea composite output signal representative of the combined audio signalfor production of an audible sound output therefrom.

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1. A method of producing signal patterns for inducing sleep in a human being by audible sounds, comprising the steps of generating an audio signal representing a familiar, repetitive, pleasing sound, generating a first modifying signal having a varying frequency and continuously sweeping said first modifying signal back-and-forth through a frequency range from about 0.8 cycles per second to 1.8 cycles per second, generating a second modifying signal having a varying frequency and continuously sweeping said second modifying signal back-and-forth through a frequency range from about 5.5 cycles per second to 6.75 cycles per second, and modifying the audio signal with said first and second swept modifying signals to produce a composite output signal representative of the modified audio signal for production of an audible sound output therefrom.
 2. A method of producing sounds for inducing sleep in a human being, comprising the steps of generating an audio signal representing a familiar, repetitive, pleasing sound, generating a first modifying signal having a varying frequency and continuously sweeping said first modifying signal back-and-forth through a frequency range from about 0.8 cycles per second to 1.8 cycles per second, generating a second modifying signal having a varying frequency and continuously sweeping said second modifying signal back-and-forth through a frequency range from about 5.5 cycles per second to 6.75 cycles per second, modifying the audio signal with said first and second swept modifying signals to produce a composite output signal; and producing an audible sound output from said composite signal for inducing sleep in an individual.
 3. A method of producing sounds for inducing sleep as defined in claim 2, including the further step of setting a timing device to automatically turn off the output signal after a pre-determined time.
 4. A method of producing sounds for inducing sleep as defined in claim 3, comprising the further step of setting the audible level of said sound output at a level to mask the ambient noise level of the environment.
 5. A method of producing signal patterns for inducing sleep in a human being, by audible sounds, comprising the steps of generating a selected audio signal chosen from a group of pre-determined audio signals, generating a first modifying signal having a varying frequency and continuously sweeping said first modifying signal back-and-forth through a frequency range from about 0.8 to 1.8 cycles per second resembling delta wave patterns occurring in a human EEG sleep pattern signal, generating a second modifying signal having a varying frequency and continuously sweeping said second modifying signal back-and-forth through a frequency range from about 5.5 to 6.75 cycles per second resembling theta wave patterns occurring in a human EEG sleep pattern signal; and modifying said selected audio signal with said first and second swept modifying signals to produce a composite output signal representation of the modified audio signal for production of an audible sound output therefrom for inducing sleep in a human being.
 6. A method of producing sounds for inducing sleep in a human being, comprising the steps of generating a selected audio signal chosen from a group of predetermined audio signals, generating a first modifying siGnal having a varying frequency and continuously sweeping said first modifying signal back-and-forth through a frequency range from about 0.8 to 1.8 cycles per second resembling delta wave patterns occurring in a human EEG sleep pattern signal, generating a second modifying signal having a varying frequency and continuously sweeping said second modifying signal back-and-forth through a frequency range from about 5.5 to 6.75 cycles per second resembling theta wave patterns occurring in a human EEG sleep pattern signal, modifying said selected audio signal with said first and second swept modifying signals to produce a composite output signal, and producing an audible sound output from said composite output signal for inducing sleep in a human being.
 7. A method of inducing sleep as defined in claim 6, comprising the further step of setting the audible level of said audible sound output at a level to mask the ambient noise level of the environment.
 8. A method of producing sounds for inducing sleep in a human being, comprising the steps of generating a composite signal representation of a familiar, repetitive, pleasing audio signal, producing a first modifying signal and continuously sweeping it back-and-forth through a frequency range from about 0.8 cycles per second 1.8 cycles per second, modulating said audio signal with said first modifying signal, producing a second modifying signal and continuously sweeping it back-and-forth through a frequency range from about 5.5 cycles per second to 6.75 cycles per second, modulating said audio signal with said second modifying signal thereby producing a composite signal representation from said audio signal and said modifying signals, and producing an audible sound output from said composite signal representation for inducing sleep in an individual.
 9. A method of producing sounds for inducing sleep as defined in claim 8, comprising the further step of setting the audible level of said audible sound output at a level to mask the ambient noise level of the environment.
 10. Apparatus for producing signal patterns for inducing sleep in a human being by audible sounds, comprising audio signal generating means for generating an audio signal representing a familiar, repetitive, pleasing sound, first and second modifying signal generators, means for varying the frequency of the signals produced by said modifying signal generators for generating a first signal having a varying frequency range from about 0.8 to 1.8 cycles per second and for concurrently generating a second modifying signal having a varying frequency which is continuously swept back-and-forth through a frequency range from about 5.5 to 6.75 cycles per second; and means for modifying the audio signal with said first and second modifying signals to produce a composite output signal representation of the modified audio signal for production of an audible sound output therefrom.
 11. Apparatus as defined in claim 10, including recording means for recording said composite output signal representation on a recording medium.
 12. Apparatus as defined in claim 10, including recording means for recording said composite output signal representation on magnetic tape recording medium.
 13. A method of producing signal patterns for inducing sleep in a human being by audible sounds, comprising the steps of generating an audio signal representing a familiar, repetitive, pleasing sound, generating a first modifying signal having a varying frequency and continuously sweeping said first modifying signal back-and-forth through the delta frequency range, generating a second modifying signal having a varying frequency and continuously sweeping said second modifying signal back-and-forth through the theta frequency range and modifying the audio signal with said first and second signals to produce a composite output signal representative of the combined audio signal for production of an audible sound output therefrom. 